: Leak Back Pressure Incorrect

11-20-05, 07:30 PM
I have a 1998 STS that has a stalling problem when stopped. Runs great otherwise.

The Technicians have put a fuel pressure gauge on and the reading of fuel pressure is OK , but found that the leak back pressure is incorrect. This leads them to beloieve the fuel pump module is faulty and needs to be replaced.

Is this a correct diagnosis and would it be the reason for my stalling problem?


11-21-05, 01:37 PM
i would say the fuel pressure regulator at first glance.

good luck

11-21-05, 01:38 PM
although this could not even be fuel related, could be bad alternator or lots of other ideas.

11-23-05, 01:10 AM
Is the "leak back pressure" you are describing the pressure in the fuel system when the key is turned off and the engine is not running??

If so , that is not likely the cause of your stalling problem. While the system is supposed to hold pressure when the engine is not running it is not that uncommon for the pressure to leak down when the engine is off. It is rarely a cause of problems but if it were it could cause hard starting, long cranks, hard starting in hot weather due to vapor lock....that sort of thing.

If the engine is stalling from an idle the fuel pressure when the engine is off is not really related to the problem I wouldn't think.

First, try cleaning the throttle body. Hold the throttle blade wide open and use carb cleaner, an old tooth brush and rag to clean the bore of the throttle body and the backside of the throttle blade.

If deposits build up over time and restrict the flow of air around the perimeter of the throttle blade it can cause stalling as the gain rate of the idle air control valve may not be great enough to compensate for the air that normally 'leaks" around the perimter of the blade when it is in the idle position.

If cleaning the throttle body doesn't cure the problem I would look at the idle air control valve in the throttle body and clean the passage that leads to the idle air control valve.